A silencer may be described as any section of a duct or pipe adapted to reduce the transmission of sound while allowing the free flow of a gas. Silencers can be broken into two fundamental groups: absorptive silencers and reactive silencers. Absorptive silencers include either fibrous or porous materials and depend on the absorptive properties of these materials to reduce noise. Absorptive silencers are most useful for noise control problems associated with high frequency spectra and their low frequency absorption increases with an increasing thickness of the absorbing material and with an increasing length of the silencer.
Reactive silencers contain no absorbing material but depend on the reflection or expansion of sound waves within a chamber to attenuate the sound. Peak attenuation occurs in the lower-frequency ranges, typically below 500 Kz. To provide a wide spectrum of attenuation, several chambers may be assembled in series.
Some silencers combine reactive and absorptive elements. However, these silencers typically are large and heavy and have some undesirable properties, such as a large resistance to motion or air within the silencer. Accordingly, difficulties in specifying a silencer for use in a particular situation are generally found when dealing with problems such as size, weight and aerodynamic pressure losses, among others, and not in providing a silencer with adequate acoustical performance.
Against this background, there exists a need in the industry to provide a novel and compact silencer.